if your in veg i would def recomend letting the temps stay high, the higher the temps are the more dense the air gets the higher the relative humidity becomes, high humidity is very crucial during the begining stages, however i think your concern should be on the temps when the lights go off, if its 60 with there on it must be dangerously low when there off, keep in mind to get the best results and most healthy plants you dont need the most perfect setup, you need the most stable setup, plants dont like a lot of changes, try to keep all elements of your enviroment at a balance, that means temps, humidity, ph, nutrients and co2, all changes you make, make them gradually, the most damage occurs when any of those elements drop too low or spike to high, plants adapt to there enviroment and thrive in consistancy, sorry if ive rambled on, i just like to spread knowledge